Lapping tool



S. H. DUGGAN Jan. 2, 1951 LAPPING TOOL 2 SheetS Sheet 1 Filed Aug. 12, 1949 $4M H. DUGGAN BY I ATTORNEY 2 Sheets-Sheet 2 s. H. DUGGAN LAPPING TOOL Jan. 2, 1951 Filed Aug. 12, 1949 m bbx INVENTOR. 3AM H. DUGGAN BY Q . zflfi/flk.

ATTORNEY Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended. April 30, 1928; 370 O. G. 757) 6 Claims.

This invention relates to improvements in abrading apparatuses, a particular purpose thereof being to lap articles of work, such as reciprocable shafting, in the longitudinal direction to avoid premature wearing out of a soft packing. In explanation of the background into which the lapping block fits, it is given as of common knowledge that shafting is ordinarily finished by shaving or grinding in a lathe or an appropriate equivalent. Each of these operations is performed circumferentially of the piece so that when it is finished its surface will have ridges and valleys extending circularly or spirally around the piece from end to end.

These ridges and valleys are present no matter how finely the shafting is finished, and they occur even though in microscopic form in a socalled mirror finish. When shafting such as this is reciprocated through a soft packing, as in the case of a hydraulic cylinder and piston assembly, the circumferential roughness of the reciprocable shaft will act like a file on the packing and wear it to an oversize so that it will soon leak and fail to hold the fluid pressure behind it.

Acknowledgment is made of the disclosure in c the United States patent to Albert M. Johnson, No. 2,163,604 of June 27, 1939, for Honing Machine, according to which an abrasive hone is also reciprccated along a workpiece, but the fact of its being a part of a machine of such proportions that the driving and indexing apparatuses have to be carried by an immobile base denies it the facilities of manual portability, instant applicability to the work and spot use as in the case where a portion of a shaft has to be treated upon the spur of a moments necessity.

Therefore, it is an object of the invention to provide a hand-size lapping tool which has all of the mechanical proficiency of its immobile prototype, is so contrived that it can be applied to the work at any selected place either for treatment full length of the piece, or spot polishing, and has an electrical driving motor which serves as a handpiece for the tool.

Another object of the invention is to provide a lapping tool wherein the reciprocation of the arcuate pieces in alternately opposite directions in respect to each other and in reference to a guide rail is a characteristic feature of the tool to the end of assuring a mechanism which works in perfect dynamic balance as it is maneuvered over the work.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accom panying drawings wherein:

Fig. 1 is a perspective view of the lapping tool, its manner of use being designated by chain lines;

Fig. 2 is a cross section taken substantially on the line 22 of Fig. 1, and

Fig. 3 is a perspective View of the eccentric roller.

The lapping tool I0 is composed of two identi cal arcuate pieces H, I2 (Fig. 2) which give the tool the sleeve form shown in Fig. 1 when assembled on the work l3. The arcuate pieces fall short of being halves because of having to provide room for a central, relative fixture consisting of the guide rail M which divides the arcuate pieces at one of their extremities, and because of the provision of a space l5 at the other extremities to prevent their rubbing against each other.

Emery cloth liners it, or some substance that will furnish an equivalent abrasive surface, fit in the hollows of the arcuate pieces, and when the latter are clamped onto the work [3 and given their characteristic reciprocatory motion'by 'operation of the motor I! the desired finish is eventually imparted to the surface of the work. A coil spring or equivalent resilient member 18 is the clamping means that holds the tool to the job to be lapped. The ends of the spring are hooked over screws 19 that are driven part way at appropriate places into the pieces Ii, l2. The spring seeks to contract to its shortest length, and in doing so exercises a pull on the arcuate pieces, assisting in their return at maximum separation during reciprocation. The heads of the screws become convenient retainers for keeping the spring ends from slipping 01f.

The ends of the emery sheets are secured to the arcuate pieces by tacks 20 driven into the confronting ends. In practice said sheets may be backed up to obtain the desired fit around the workpiece. For example, should it happen that the bore of the tool is so much oversize that the resulting loose fit 0n the work will fail in producing an adequate lapping action, pieces of shim stock will be inserted behind the emery sheets to make the required size.

A coupling 2| near each end of the tool connects the arcuate pieces ll, I2 to the guide rail, but is so made that said pieces can be reciprocated independently of each other and in reference to the guide rail. Said coupling, momentarily confining the description to only one, consists of a bracket 22 which is fastened down on the guide rail by screws so as to become a fixture on it. Upstanding ears 23 on the ends of the bracket carry a hinge pin 24 with screw threads on one end and a screwdriver slot in the other. The hinge pin is driven into one of the ears and thus provides a hinge mount for the knuckles 25 that were previously slid upon it.

The hinge knuckles are parts of metal straps 26 that are shaped to fit the outsides of the pieces I I, 12 to which they are fastened by screws. The straps are located in offset relationship, and the hinge pin is long enough to provide enough room for the reciprocation of the sleeve pieces. The knuckles should not strike either each other or the upstanding ears.

As already pointed out, the driving power for the tool is derived from the motor H. The shaft of the latter has a coupling 21 through which attachment is made to the spindle 28 of a roller 29. This roller consists of two eccentrics 3!], 180 apart and separated by circular flanges which are parts of a one-piece structure. The inner end of the spindle, in other words the end opposite to where the motor coupling is attached, has bearing in;

a bushing 38 that is sunk through a wear plate 32 then into the guide rail. A bracket 33 holds the eccentric roller down to its bearing and furnishes the lateral support necessary to keep the spindle true.

It is readily understood that when the current is turned on there will be rotation of the eccentrics. Their motion is imparted to the sleeve pieces through two forks 34, the levels of which are such as embrace the respective eccentrics midway of their heights. The forks are the free terminal parts of straps which, like the hinge straps, are fastened down against the outside of the sleeve pieces. The motion, then is a continuous shifting of the arcuate pieces, and consists of simultaneous longitudinal movements in alternately opposite directions, serving to give the tool the dynamic balance necessary to its wielding as a hand tool.

Reverting to the abrasive lining of the latter, it is observed in Fig. 2 that the arcuate formation of the sleeve pieces ll, I2 is matched by a crossconcavity on the inner side of the guide rail. A strip 36 of emery cloth is tacked along its edges to the lateral sides of the guide rail, and furnishes a practical continuation of the cloth liners it.

In operation, the arcuate pieces I l, 82 are placed around the work I 3 to he lapped, the opening and closing movement taking place on the hinge couplings 2|. Thereupon the spring I8 is hooked in place to keep the sleeve intact and to supply the requisite clamping pressure. The motor H is used as a handpiecc, and when the cur rent is turned on the pieces I I, i2 are reciprceated in reference to both the motor and to the guide rail by which the motor is carried.

The tool can be said to comprise a handpiece consisting of the motor and guide rail, and the reciprocably carried sleeve pieces M, 2. The

double eccentric 35 causes rapid reciprocation of the abrasive sections of the tool, and by an appropriate handling of the tool the work can be lapped from end to end or at any particular place where the lapping is intended to be localized.

At this point it must be added that the designation of the pieces I l, l2 as arcuate both in the description and claims is largely a matter of convenience. In most instances the tool is used for lapping cylindrical shafting, but the cross-sectional shape could be other than round. A fiat i sided object could be lapped by an appropriate configuration of the tool, for instance, a crosssectionally square shaft would require a boxshaped tool instead of a sleeve.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understcod that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Vihat is claimed is:

1. A lapping tool comprising a work-embracing sleeve consisting of a guide rail and a pair or arcuate pieces, said guide rail and arcuate pieces having an abrasive lining, couplings hingedly and reciprocably connecting the arcuate pieces to the guide rail, means carried by the guide 'rail for producing reciprocatory movement, andmeans carried by each of the arcuate pieces being operatively connected to the foregoing means.

2. A lapping tool comprising a work-embracsleeve consisting of a guide rail and a pair of arcuate piecessaid guide rail and arcuate pieces having an abrasive lining, couplings hingedly and reciprocably connecting the arcuate pieces to the guide rail, a two component eccentric and driving motor therefor being carried by the guide rail for producing reciprocatory movement, and afork carried by each of the arcuate pieces and embracing the respective components of the eccentric.

S. A lapping tool comprising a manually ma neuverable handpiece consisting of an electric motor with a shaft, a guide rail carrying means for imparting reciprocation which means is coupled to the motor shaft to derive its movement from the motor, arcuate and abrasive work-embracing pieces having couplings hingedly and reciprocably connecting them to the guide rail, and members extending from each of the arcuate pieces into operative engagement with the reciprocation-imparting means.

e. A lapping tool comprising a work-embracing sleeve consisting of a guide rail and a pair of arcuate pieces, said guide rail and arcuate pieces having an abrasive lining, couplings between the arcuate pieces and the guide rail, each coupling consisting of a pin afiixed to the guide rail and straps on the arcuate pieces with knuckles slidably and hingedly connected to the hinge pin, a spindle journa'led on the guide rail, said spindle having a double eccentric, 'a motor having a shaft coupled to the spindle to rotate the spindle and eccentrics, and means to translate the rotation of the spindle into reciprocation of the arcuate pieces, said means consisting of forks carried by said pieces and embracing the respective eccentrics.

5. A hand-wieldable lapping tool comprising a work-embracing sleeve consisting of a pair of arcuate pieces and a fixture to which they are relatively shiftable, said arcuate pieces and fixture having an abrasive lining, couplings hingedly and reciprocably connecting the arcuate pieces to said fixture, and means mutually carried by the fixture and arcuate pieces for the arcuate pieces with simultaneous longitudinal reciprocations in respect to the fixture in alternately opposite directions for dynamic balance of the tool.

6. A hand-wieldable lapping tool comprising a work-embracing sleeve consisting of a pair of arcuate pieces, a rail situated between the arouate pieces at one of their extremities in the longitudinal direction of the arcs, said arcuate pieces and the rail having an abrasive lining, couplings hingedly and reciprocably connecting the arcuate pieces to said rail, means mutually carried by the rail and arcuate pieces for shifting the arcuate pieces with simultaneous 1ongitudinal reciprocations in respect to the rail in a1- ternately opposite directions, and a resilient member attached at its ends to the other extremities of the arcuate pieces to keep the pieces assembled on the work and to assist with a return pull at maximum separation of the pieces during reciprocation.

SAM H. DUGGAN.

No references cited 

